28 April 2011

Fresh from the news that his US$500m arched design for the Margaret McDermott Bridge in Dallas is to be dropped due to its excessive cost, Santiago Calatrava has seen another bridge project cancelled.

This one was for Denver International Airport, for which Calatrava is already designing a new terminal building. His planned 189m span arch bridge, pictured below, was intended to form a spectacular gateway to the airport, but has been ditched, again on cost grounds. Latest reports give a cost of US$22m, but it's not entirely clear if this is correct, earlier reports were talking about a US$60m bill for the bridge.

It would be unfair to suggest there is any kind of trend here.

Reports that Calatrava's World Trade Center Transport Hub in New York may see its cost rise from US$2.2bn to $3.8bn are clearly unrelated. And it would be simply churlish to recall that Calatrava originally proposed not one but two Alamillo bridges in Seville in Spain - one being omitted when the costs came in. His footbridge in Venice was completed with the vision unaltered, although opening ceremonies were cancelled due to fear of protests (possibly connected to the near doubling in its budget over time).

27 April 2011

For those unfamiliar with the term "urban exploration", it refers to the practice of treating the urban environment as if it were a wilderness, full of spectacular and interesting things which lie undiscovered, or at least not yet experienced, many of them hazardous and difficult to access. It often involves going places that are expressly off-limits to the public: sewer tunnels, derelict industrial sites, catacombs, and the normally inaccessible parts of occupied buildings.

The Happy Pontist has in the past indulged in the activity, although only in a very minor way. My work has also often given me access to places that would clearly interest urban explorers - underground rivers, derelict structures, and, of course, numerous bridges.

Serious urban explorers post details of their exploits online (anonymously, of course), and they are often highly skilled photographers, as can be seen from a few examples I've located which relate to bridges. I'm not sure why all these are in the north of England and Wales, these are just what I've found from some quick searches of the online urban exploration forums.

I'm not reproducing any of the photos here, as I suspect none of the participants are looking for wider publicity, but it really is worth visiting the websites for some spectacular and unusual views.

Lowry Footbridge, Salford
This is a lifting pedestrian bridge which I've reported on previously. This report gives a good impression of the view from the top, but this one combines stunning photography with images of people clearly totally bereft of fear.

Warrington Transporter Bridge
One of only three transporter bridges in the UK, the Warrington structure is the only one no longer in use, and has become sufficiently derelict to make it onto English Heritage's "buildings at risk" register. Although no longer officially in use, it's good to see it has had at least one daytime visitor, and one at night. The reporters are commendably concerned to warn others about the perilous state of the rotten wooden walkways. It's a real shame the bridge no longer has any obvious use which might justify investing in refurbishment.

Britannia Bridge, Anglesey
The present Britannia Bridge, a 1970s reconstruction following fire damage to Stephenson's original bridge, is one of the less "precarious" bridges here. Indeed the arches seem well equipped with maintenance walkways, making the photographs of an unauthorised site visit noticeably less terrifying than some of the others.

Wearmouth Bridge, Sunderland
These pictures are almost too terrifying to look at, but also quite stunning. Unlike the other bridges above, the steel arch Wearmouth Bridge doesn't have dedicated maintenance ladders and walkways. I've been up one or two vertigo-inducing structures in my time, and on occasion been on parts of a bridge which don't feel particularly safe, but nothing like this. The intrepid correspondent walked up the top surface of the arches, which are unprotected by any form of railings or guide cable (or indeed any measures to deter the foolhardy).

24 April 2011

Frame and Form has published images of the next set of shortlisted entries to the 2011 Footbridge Awards - the "aesthetics" category for bridges spanning between 30m and 75m. Again, please see their blog post for the images.

I covered the Knokke Heist Footbridge here near the end of 2009. Designed by Ney & Partners, it's a tour-de-force of structural design, synthesising a number of individually great ideas and producing something which is spectacular but still graceful.

Taking the bending diagram for a three-span continuous beam as their starting point, they stripped away unnecessary material stage by stage to evolve a structure which is a unique hybrid of suspension bridge, stayed bridge, and steel girder. It borrows from the form-finding techniques of structural fabric design, with a thin steel skin draped between points of support, cradling the bridge deck and providing a seemingly effortless response to the three dimensional geometry and load requirements.

In many ways, it's an inverted version of Robert Maillart's Tavanasa Bridge. I admire it for its undeniable panache but also for the ability to take a challenging concept and follow it through what must have been a very demanding fabrication and construction process without losing anything to pragmatist compromise.

Barcelona's Sant Fruitós Footbridge, designed by Pedelta, pairs the classic inclined arch typology with the use of stainless steel and GFRP elements. I always find this kind of design slightly forced when, as here, the deck is straight in plan, as the arch inclination has no real structural justification, it's just an affectation intended to add interest to what would otherwise be a fairly straightforward footbridge over a highway.

Despite the awkwardness of a lift tower and staircase at one end, the design doesn't seem unbalanced, and is a good example of its kind. It's interesting to compare Calatrava's La Devesa Bridge at Ripoli, which also has an inclined arch and the issue of very different approach levels to resolve. The Calatrava Bridge has the elegant combination of a cantilevering end support with a staircase, killing two birds with one stone, but the use of cables rather than "bracket arms" at Sant Fruitós gives a lighter and hence more pleasant appearance overall.

The Paloma Footbridge is quite a different proposition. Spanning a highway in Madrid, this bridge is curved in plan, but eschews the counterbalancing cable-stayed or inclined arch support system that may suggest in favour of a warren truss along only the outer edge of the deck. It isn't entirely unique, and reminds me in concept of the Mancunian Way Footbridge, which also had a truss along its curved outer edge.

On the Paloma structure, the main truss appears to be stabilised by a secondary truss connected to its top chord, and sitting flat to provide stiffness against out-of-plane movement of the main truss. It's a neat conception, mainly because it also carries a canopy and hence provides some level of shade and shelter.

What I like about this bridge is not just the interesting structural form, but the quality of the detailing, which looks to be quite impeccable from the photos available.

The Sant Fruitós inclined arch has a cousin on the shortlist, the Riverside Bridge in Cambridge. It was designed by Ramboll, and adopts the white colour that so many of this kind of bridge seem to share. Its main span over the River Cam comprises an inclined tubular steel arch supporting on one side the footway deck, and on the other a cycleway deck. The two decks are carried by transverse "wishbone" members, and supplementary cables, which balance the loads such that out-of-plane bending of the main arch is minimised.

I'm keen to pay it a visit, but based on photographs, it seems only partially successful. The split deck, which seems clever at first, also complicates the overall geometry, multiplying the balustrades and eliminating the simple elegance which inclined arches can normally boast.

I've covered New Zealand's Te Rewa Rewa Bridge here before, and have little to add to my previous comments. The asymmetry of its arch ribs has no structural logic, but seems visually compelling. The detailing lifts it beyond dozens of minimalist Calatrava clones, such as the way the ribs extend above the arch spine. It's definitely one of my favourite bridges on the shortlist.

RFR's Lyon Confluence Bridge is a fine riposte to the structural showmanship of so many post-Millennium footbridges. Timber decking sits on a relatively straightforward tubular steel arch structure, made very slender in line with a number of other recent RFR designs. Indeed, it looks so slender that I wonder whether a minor impact from a boat wouldn't be enough to bring it down, but presumably they will have considered that.

I can find no information on the Butarque Footbridge, in Spain, online, other than the photograph provided at Frame and Form. It shows a bridge which appears to have a deck with a triangular cross-section, supporting a rail-less balustrade. If anyone can point me to any other images, please leave details using the comments link below.

21 April 2011

Excellent! Those spiffy bloggers at Frame and Form have provided some images of the structures shortlisted for these awards, kindly saving me the bother and making it easier for me to comment on some of the entrants. So far, they've posted pictures of the entries under the short span (below 30 metres) / aesthetics category - go to their post for the images, I won't repost them here.

Judged purely on aesthetics, I'd want the CastlefordFootbridge to win. It's a beautifully well-judged structure, tip-toeing gracefully across the river like a slow-motion ballerina, artful and expressive without ever having to be inappropriately demonstrative. It doesn't exhibit the need to show off, but its sinuous layout, use of the main girders as benches, and extensive presence of timber, all offer a humanistic approach to bridge design that's entirely appropriate to its setting.

The Bracklinn Falls Bridge, at Callander in Scotland is another structure which is undoubtedly interesting but not necessarily "beautiful". I plan to visit it at some point and cover it in more detail. The combination of huge, rustic tree trunks with more modern timber and steel elements is striking, as is the setting. However, the triangular elevation, while robustly pragmatic, has no finesse to it.

I find the Buitengragt Pedestrian Bridge, in Cape Town, South Africa, more disconcerting than attractive. The deck is supported by stays from an inverted steel pyramid. It gives an impression of instability, and its hard to see why a stayed bridge was justified for such a short span at all.

The Yale Hillhouse Pedestrian Bridges, in Connecticut, USA, are not my favourite bridges for overall appearance, but I hugely admire their ingenuity. I recall seeing these previously, and the perforated, corrugated steel webs remain a delight. The corrugations help to stiffen the upper member of the side trusses against buckling, as well as preventing buckling of the webs themselves, while allowing the web plate to be very thin. The perforations hark back to Ithiel Towne's 19th century lattice trusses, one of many old truss designs ripe for reinvention.

Together, these two features significantly reduce the weight of the girders (although clearly only at the expense of much increased fabrication costs). An article in the ASCE's Civil Engineering magazine explains more. It's a shame this design isn't in the "technical short span" category, it's a very impressive piece of structural engineering.

Gustav Lindenthal Medal
North Arm Fraser Crossing, British Columbia, Canada, for an outstanding structure that is also aesthetically and environmentally pleasing

Eugene C. Figg, Jr. Medal
Mike O'Callaghan-Pat Tillman Memorial (Hoover Dam By-Pass) Bridge, connecting Arizona and Nevada, for Signature Bridges, recognising a single recent outstanding achievement for bridge engineering, which is considered an icon to the community for which it is designed

Arthur C. Hayden Medal
Te Rewa Rewa Bridge in New Plymouth, New Zealand, recognising a single recent outstanding achievement in bridge engineering demonstrating vision and innovation in special use bridges

Engineering Excellence Award
FHWA Manual "Analysis and Design of Skewed and Curved Steel Bridges with LRFD Reference Manual", awarded to be special and beyond the traditional guidelines of the medal categories

James C. Cooper Student Award
Behrouz Ahafei , University of California at Irvine, for undergraduate and graduate students who demonstrate an interest and passion for bridge engineering

The IBC presents itself as "the" international bridge conference, but is generally dominated by North American attendance with a strong Asia-Pacific presence. It's nice to see the awards are more wide-ranging, although possibly still somewhat inward-looking - is an FHWA Manual really the most excellent example of bridge engineering worldwide in the last year?

Having ditched the Calatrava arches, they are reportedly going for a less extravagant US$220m project, which still seems grossly inflated for a bridge of this size. What's particularly striking, however, is the news that they want to retain Calatrava to design only the bicycle and pedestrian elements of the cut-price design, and will be paying him some US$10.7m to do so - US$2.1m left over from his incomplete arch bridge contract, US$3.5m of Dallas funds, and an amazing US$5m of donations from an anonymous philanthropist.

There is clearly an argument that it's worth paying over the odds for the prestige of a brand name designer, but with the iconic element of the bridge gone, it's hard to credit why anyone would pay so much money simply to design its footways.

Million pound bombshell could wreck Perth bridge plan
This project for a Sustrans-supported cycle bridge near Perth had already been struggling with land purchase issues, but having seemingly resolved those, it has now been hit by the design consultant's announcement that it may cost £1m more than expected - extra money that simply isn't in the budget. Indeed, it's not even that simple. An original estimate of £1.8m for construction costs was apparently based on a simple "per square metre" figure. However, according to the Perthshire Advertiser, an additional £755k for craneage costs was later added, with the capital cost rising first to £3.5m and then eventually to £5.25m.

The bridge design consists of three arch spans, 200m long in total, supporting a 3m wide deck. So, for the original £1.8m estimate, that works out at £3,000 per square metre, which is cheap for a landmark bridge, but certainly achievable for a footbridge with no unusual construction issues. The latest £5.25m estimate would work out at £8,750 per square metre, which is expensive for the relatively straightforward structural form, but not unreasonable given the difficult access for construction in a wide river.

What will happen next is unclear - I would guess the scheme will be dropped completely, although the simple exercise of inviting preliminary tenders or getting an ECI contractor on board might help increase cost certainty.

This could be an interesting talk, for anyone in the London area on 5th May.

The IABSE British Group's Annual Lecture is being presented by Keith Brownlie of Wilkinson Eyre, the venue is the Institution of Structural Engineers, near Victoria, with the lecture starting at 6pm. Full details are available online, including a flyer.

Brownlie has been prominently involved in many of Wilkinson Eyre's landmark bridge designs, including the Gateshead Millennium Bridge. The talk will address the influence of the Millennium structures on his design team's more recent projects, and "consider the bridge design market as it pulls clear of the influence of the Millennium".

I would expect it to be very interesting, as the turn of the Millennium and the flurry of design contests and investment in icons which followed was simultaneously a short-lived bubble and also a source of inspiration to bridge promoters everywhere. Was it a brief golden age, or a period which has permanently changed design aspirations, options for bridge procurement, and the way bridge design teams operate?

I'll be attending the announcement of the winners, and will hopefully find time to cover them in more detail here when that happens. I haven't yet had a chance to look for details of the several shortlisted bridges which are unfamiliar to me, so I won't hazard any guesses as to which bridges will do well in the awards.

08 April 2011

I've reported extensively on the awkward progress of Santiago Calatrava's Peace Bridge in Calgary, with my last post in October noting the bridge was delayed until this January. Then, January came and went with no news, although it's now reported that several of the bridge welds have failed an independent inspection.

The scheme initially achieved bad publicity courtesy of the City of Calgary's decision to break its own procurement rules and award Calatrava the CAN$3m design contract without any competition. Unsurprisingly, tenders came in above budget, for a scheme which was already one of the most expensive footbridges ever conceived. The key steelwork fabrication sub-contract was awarded to a Spanish firm, with Canadian suppliers judged either too expensive or lacking the requisite expertise, prompting more grumbling from the locals.

It's therefore doubly embarrassing now that welds made in Spain have failed to pass muster once shipped to Canada and subjected to independent testing. It's not entirely clear what the welding flaws are, with the contractor saying:

"There are probably some deficiencies in the welding, but it could just be different testing results and specifications in Spain. Now we need to make sure there is conformity."

"We're not seeing an even joint between joining the two plates of metal."

In some ways, it's astounding that the welds were not properly tested before the steelwork was shipped, but in the real world it is not unusual for something like this to go wrong, even on such a prestige project. Unless it turns out that it is all a matter of misinterpreting the standards for weld testing, then someone clearly needs a major slap on the wrist. As the welds are re-tested and debated, the date for completion of the bridge slips further back, such that now nobody is even confident to say it will be completed this year.

At least the client's costs should not overrun - the risk of errors in manufacture lies with the contractor under the D&B contract. That's on the assumption that the problem is not with the original client specification, of course.

Faced with questions on who is to blame, the Calgary Herald turns, with dizzying irrelevance, to "local architects", who say that the simple matter of getting welds right is unsurprisingly difficult on such complex work. And they should know, right?

Officials and politicians seem to be queueing up to make sure the blame is placed with the contractor rather than the designer, and I have some sympathy with this. However, I've seen the welds on a Calatrava bridge - enormous, chunky, beasts of metal deposition, all laboriously hand-welded because of the highly curved and geometrically complex joints required. While the contractor ought to know what they are taking on, it also must be recognised that the designer has a part to play in coming up with a structural form which is buildable safely, economically, and which makes high quality work straightforward rather than a headache. There is, ultimately, a price to be paid for the Peace Bridge's spectacularly daft helical geometry, and this is it.

While most commenters are sanguine about what has happened, I'd recommend the inimitable Rick Bell of the Calgary Sun for the contrarian view, that it's an almighty balls-up borne of the arrogance of politicians and experts.

While the Peace Bridge saga drags ever more slowly on, it's nice to see that Calgary's other landmark footbridge, the St Patrick's Island Bridge, designed by RFR, is making steady progress, having just received unanimous approval from a city committee. I hope Calgary's desire to make it out of bits of old oil pipeline doesn't lead to trouble down the line.

Meanwhile, in Dallas, another Calatrava design is bogged down by an unaffordable price tag and a lack of funding to match. At least the reported US$8m design fee appears safe.

And just to conclude, proposals to add a second deck to Calatrava's Sundial Bridge, in California, have hit a major hurdle as well, although in this case they've been blocked neither by cost nor cock-up, but simply by being exposed as an April Fool's Day story.

04 April 2011

A mixture of lack of time on my part, and a lack of interesting bridge news, means it is all quiet on the pontist front, and likely to remain so for a little while, what with workload and Easter holidays on the way. I have a few posts in gestation but they will take some time to get ready.

Rather than whistling aimlessly and drumming fingers impatiently on the (virtual) table, here's an open thread.

Is there some bridge-related news I've missed?

A topic you'd like me to cover in the future?

Something you meant to comment on previously but never got around to?

Here's your chance: just click the Comment link at the bottom of this post!